Intervention blowout preventer and well intervention tool

ABSTRACT

The present invention relates to an intervention blowout preventer ( 1 ) for being mounted on a well head ( 2 ) or a Christmas tree, comprising a plurality of valves ( 3, 4 ) arranged in fluid communication with each other, connected and forming a tubular pipe ( 5 ) enclosing a cavity being in fluid communication with the well head when the intervention blowout preventer is mounted onto the well head and at least one plug ( 37 ) in the well head has been removed, wherein the intervention blowout preventer further comprises a pressure reducing system ( 1 ) comprising a chamber ( 6 ) and a piston ( 7 ) arranged inside the chamber dividing the chamber into a first chamber part ( 8 ) and a second chamber part ( 9 ), the first chamber part being in fluid communication with the cavity and the second chamber part being filled with a compressible fluid, such as gas. Furthermore, the invention relates to a well intervention tool ( 100 ), a well intervention system ( 200 ) and a well intervention method.

FIELD OF THE INVENTION

The present invention relates to an intervention blowout preventer for being mounted on a well head, comprising a plurality of valves arranged in fluid communication with each other, connected and forming a tubular pipe enclosing a cavity being in fluid communication with the well head when the blowout preventer is mounted onto the well head and at least one plug in the well head has been removed. Furthermore, the invention relates to a well intervention tool, a well intervention system and a well intervention method.

BACKGROUND ART

Before intervening a well, the crown plugs need to be pulled in order to provide access to the well. The well may be situated 2000 metres below the surface of the sea, resulting in a substantial amount of pressure acting upon the plug to be pulled, said pressure often being larger than the pressure in the well. The tool for pulling the plug then has to provide a force overcoming the pressure from the water column above the plug and often also the drag force applied from the lower pressure in the well.

Some pulling tools anchor up inside the lubricator connected to the BOP being on top of the well head. In order to provide the force needed to pull a plug in deep water wells, the amount of force applied by the anchors to the lubricator requires a redesign of the lubricator in order for the lubricator to be able to withstand such anchoring force.

SUMMARY OF THE INVENTION

It is an object of the present invention to wholly or partly overcome the above disadvantages and drawbacks of the prior art. More specifically, it is an object to provide an improved blowout preventer or intervention tool making it easier to pull a plug in the well head or Christmas tree, such as a crown plug.

The above objects, together with numerous other objects, advantages, and features, which will become evident from the below description, are accomplished by a solution in accordance with the present invention by an intervention blowout preventer for being mounted on a well head or a Christmas tree, comprising:

-   -   a plurality of valves arranged in fluid communication with each         other, connected and forming a tubular pipe enclosing a cavity         being in fluid communication with the well head when the         intervention blowout preventer is mounted onto the well head and         at least one plug in the well head has been removed,         wherein the intervention blowout preventer further comprises a         chamber and a piston arranged inside the chamber dividing the         chamber into a first chamber part and a second chamber part, the         first chamber part being in fluid communication with the cavity         and the second chamber part being filled with a compressible         fluid, such as gas.

By having such pressure reducing system in the form of the chamber and the piston, the pressure inside the intervention blowout preventer can be substantially reduced, reducing the amount of force needed to pull the plug.

Also, the cavity may have a first pressure and the intervention blowout preventer may further comprise a control device, such as a valve, for controlling the pressure in the cavity by letting fluid in the cavity into the first chamber part.

In one embodiment, the piston may be slidably arranged on a shaft arranged inside the chamber.

Furthermore, the first chamber part may be connected with the cavity by means of a flow channel.

Hereby, the chamber can be arranged at a distance from the tubular part of the intervention blowout preventer and may be easily implemented in existing blowout preventers, and the control device may be mounted on the flow channel so that the control device can be operated by an ROV, or manually or even remotely.

The intervention blowout preventer as described above may further comprise a control unit comprising a storage device, and a communication unit for communicating with the control device.

Moreover, the intervention blowout preventer as described above may comprise a sensor for sensing a pressure in the cavity.

Further, the pressure reducing system may comprise a pump for pumping fluid from the cavity into the first chamber part.

In one embodiment, the chamber may be an accumulator.

Also, the pressure reducing system may comprise an accumulator.

Said accumulator may comprise the piston, a bladder or a diaphragm.

The present invention also relates to a well intervention tool intended to be arranged in a lubricator for pulling a plug in a top part of a well head or a Christmas tree of a well for entering the well, the well head having an axial extension, comprising:

-   -   a connection pulling unit having a connection unit for         connection to the plug,     -   a stroking tool having a tool housing and being connected to the         connection pulling unit and providing an axial movement along         the axial extension, and     -   a fixation unit for fixating the stroking tool in relation to         the well head so that the axial movement of the stroking tool         pulls the plug out of the well head, wherein the stroking tool         comprises a chamber and a piston arranged inside the chamber         dividing the chamber into a first chamber part and a second         chamber part, the first chamber part being in fluid         communication with an opening in the tool housing and the second         chamber part being filled with a compressible fluid, such as         gas.

In one embodiment, the stroking tool may further comprise a control device, such as a valve, for letting fluid in through the opening of the housing into the first chamber part.

Moreover, the connection pulling unit may be a GS pulling tool.

Also, the piston may be slidably arranged on a shaft arranged inside the chamber.

Furthermore, the control device may be arranged in the opening.

In addition, the stroking tool may be connected with the connection pulling unit by means of a stroker shaft.

In one embodiment, the fixating unit may comprise an anchoring section having anchors moving radially from the tool towards an inside wall of the lubricator.

In another embodiment, the fixating unit may be a tubular section surrounding part of the connection pulling tool for abutting a top part of the well head.

Further, the connection unit of the connection pulling unit may comprise latches for engaging inside the plug to be pulled.

The intervention blowout preventer according to the present invention may further comprise a control unit comprising the storage device, and a communication unit for communicating with the control device.

Furthermore, the present invention relates to a well intervention system comprising:

-   -   an intervention blowout preventer according to the invention for         connection onto a well head,     -   a lubricator connectable to the intervention blowout preventer,         and     -   an intervention tool according to the invention arranged inside         the lubricator for pulling the plug in a top part of a well head         or a Christmas tree of a well for entering the well.

In one embodiment, the lubricator may be closed off at a first end by a blind cap.

In another embodiment, the lubricator may comprise a lubricator valve arranged to close off the lubricator at a second end of the lubricator opposite a first end.

Moreover, a shear ram valve may be connected with the lubricator valve.

Also, the intervention system may comprise a disconnection unit arranged between the lubricator valve and the intervention blowout preventer for disconnecting a part of the system.

Further, the intervention tool may comprise a driving section, such as a downhole tractor.

Additionally, the intervention tool may be wireless and driven only by an internal power source.

By having a wireless intervention tool, a grease connector head is not needed in the end of the lubricator.

Said intervention tool may comprise an inductive coupling for charging or recharging power.

Also, the intervention system may further comprise a vehicle which is remotely operated.

Finally, the present invention relates to a well intervention method comprising the steps of:

-   -   arranging the well intervention tool as described above inside a         lubricator,     -   connecting the lubricator on the intervention blowout preventer         as described above,     -   connecting the well intervention tool to the plug,     -   equalising a pressure inside the cavity of the intervention         blowout preventer with a pressure in the well below the plug,         and     -   pulling the plug in a top part of a well head or a Christmas         tree of a well.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention and its many advantages will be described in more detail below with reference to the accompanying schematic drawings, which for the purpose of illustration show some non-limiting embodiments and in which

FIG. 1 shows an intervention blowout preventer mounted on a well head,

FIG. 2 shows a well intervention system comprising a well intervention tool mounted on the intervention blowout preventer,

FIG. 3 shows another embodiment of the well intervention tool,

FIG. 4 shows another embodiment of the intervention blowout preventer, and

FIG. 5 shows yet another embodiment of the intervention blowout preventer.

All the figures are highly schematic and not necessarily to scale, and they show only those parts which are necessary in order to elucidate the invention, other parts being omitted or merely suggested.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an intervention blowout preventer 1 mounted to a top part 22 of the well head 2 arranged on the seabed on deep water. The intervention blowout preventer 1 comprises a plurality of valves 3, 4 arranged on top of each other, and thus in fluid communication with each other. The first valve is an annular valve 3 and the other valve may be a ram valve 4. The valves 3, 4 are connected and form part of a tubular pipe 5. At the end closest to the rams, the tubular pipe is connected with the well head 2, and at the other end, the tubular pipe may be connected with a lubricator 20 comprising a well intervention tool 100 illustrated by dotted lines. Thus, the tubular pipe 5 encloses a cavity 10 which is in fluid communication with the well head when the intervention blowout preventer is 1 mounted onto the well head 2 and at least one plug 37 in the well head has been removed by means of an intervention tool 100.

The lubricator 20 is arranged on top of the intervention blowout preventer 1, said lubricator being arranged comprising the intervention tool capable of pulling the plug 37 and providing access to the well for a subsequent tool. The intervention tool 100 is powered by means of a wireline 24 extending through a grease injection head 21.

The intervention blowout preventer 1 further comprises a pressure reducing system 120 in the form of a chamber 6 and a piston 7. The piston 7 is arranged inside the chamber dividing the chamber into a first chamber part 8 and a second chamber part 9. The first chamber part 8 is in fluid communication with the cavity and the second chamber part 9 is filled with a compressible fluid, such as gas. The chamber 6 is connected with the tubular pipe 5 by means of a flow channel 15 providing the fluid communication between the cavity and the first chamber part. A control device 11, such as a valve, is arranged in the flow channel 15 for controlling the flow of fluid into the first chamber part 8. The control device 11 is closed when the lubricator 20 is connecting and subsequently, the control device 11 is opened, hence letting fluid from the cavity into the first chamber part 8, decreasing the pressure inside the intervention blowout preventer 1 and the lubricator 20. By decreasing the pressure inside the intervention blowout preventer 1, the force acting on the plug 37 is also decreased substantially and the plug 37 is thus easier to pull.

By having a pressure reducing system 120 in the form of the chamber 6 with the piston 7, it is thus possible to equalise the pressure over the well head 2, so that the pressure in the intervention blowout preventer 1 can be adjusted to be substantially the same as the pressure in the well below the plug or plugs.

Inside the chamber, the piston is slidably arranged on a shaft 12 which is also inside the chamber. In this way, the movement of the piston is controlled so that the piston does not tilt and jam if further movement of the piston is needed. When the fluid is let into the first chamber part, the gas inside the second chamber part is compressed, increasing the volume of the first chamber part as it is filled with fluid.

The capacity of the chamber is typically 5 litres, preferably 8 litres or more preferably 10 litres, or more.

The control device 11 may also comprise a motor adjusting the control device or the position of the valve in order to let more or less fluid into the first chamber, or even stop the fluid from entering.

By having a flow channel 15 connecting the chamber with the cavity, the chamber can be arranged at a distance from the tubular part of the intervention blowout preventer and is easily implemented in existing blowout preventers.

Furthermore, the control device 11 can be mounted on the flow channel so that the control device can be operated by an ROV, or manually or even remotely.

The intervention blowout preventer 1 may further comprise a control unit 38 comprising the storage device, and/or a communication unit for communicating with the control device 11. The intervention blowout preventer 1 may further comprise a sensor for sensing a pressure in the cavity and the current pressure can be sent through the communication unit or stored for later use. Depending on the pressure, the control device 11 is actuated to either let more fluid into the first chamber part 8 or decrease the flow thereto.

FIG. 2 shows a well intervention tool 100 for pulling the plug 37, such as a crown plug, in a top part 23 of a well head 2 in order to be able to enter the well. The intervention tool 100 comprises a connection pulling unit 50, such as a GS pulling tool having a connection unit 51 matching the connection of the plug 37. When performing a pulling operation, the intervention tool 100 is arranged in a lubricator connected to the top of the intervention blowout preventer 1. The intervention tool 100 comprises a fixation unit 54 for fixating the stroking tool 52 in relation to the well head 2 so that the axial movement of the stroking tool 52 pulls the plug 37 out of the well head 2. The fixation unit 54 comprises an anchoring section having anchors 57 moving radially from the tool towards an inside wall of the lubricator 20 as shown in FIG. 2. In another embodiment, the fixation unit 54 comprises a tubular section surrounding part of the connection pulling tool for abutting the top part 23 of the well head 2 as shown in FIG. 3.

The stroking 52 tool comprises a tool housing 53 in which a pressure reducing system 120 in the form of a chamber 106 and a piston 107 is arranged. The piston 107 is arranged in a sliding manner on a shaft 112 inside the chamber, dividing the chamber into a first chamber part 108 and a second chamber part 109. The first chamber part 108 is in fluid communication with an opening 113 in the tool housing 52 and thus in fluid communication with fluid in the lubricator. The second chamber part 109 is filled with a compressible fluid, such as gas. In order to reduce the amount of force needed to pull a plug 37, the pressure inside the lubricator is reduced after the lubricator has been connected with the well head 2. The stroking tool 52 further comprises a control device 111, such as a valve, for controlling the pressure in the lubricator 20 by controlling the amount of fluid let into the first chamber part 108. By letting fluid from the lubricator into the first chamber part 108, the piston moves and the gas in the second chamber part 109 is compressed and the pressure inside the lubricator is reduced. By reducing the pressure in the lubricator 20, the amount of force needed to pull the plug is also reduced substantially, and thus the anchoring force needed is reduced accordingly. By reducing the anchoring force, a standard lubricator can be used to anchor up and the plug can thus be pulled by a stroking tool.

As shown in FIG. 2, the connection of the plug 37 to be pulled comprises a female connection and the connection unit 51 of the connection pulling unit 50 is shaped as a male connection with latches matching the female connection. The intervention tool 100 further comprises a stroking tool 52 connected to the connection pulling unit and providing an axial movement along the axial extension for moving the male connection unit into engagement with the female connection of the plug 37. Once the male-shaped connection unit 51 engages the female connection of the plug, the stroking tool moves a first part of the connection pulling unit 50 in relation to a second part in order to move the latches radially outwards.

As can be seen, the control device 112 is arranged in the opening 111, but may be arranged in any suitable manner.

The stroking tool 52 is connected with the connection pulling unit 50 by means of a stroker shaft 55 and a threaded connection or a conventional male/female connection.

The intervention blowout preventer 1 may comprise a control unit comprising a storage device, and a communication unit for communicating with the control device 111. In this way, the control device 111 can be controlled from surface.

FIG. 2 further shows a well intervention system 200 comprising any conventional blowout preventer or the intervention blowout preventer mentioned above and a lubricator 20 connectable to the intervention blowout preventer in which the intervention tool 100 is arranged in order to pull the plug 37. Normally, the intervention tool needs to pull two plugs as shown in FIG. 3, which may be done in two runs. A second intervention tool inside a second lubricator may be arranged in the vicinity of the well head, ready to be connected when the first plug is pulled.

The pressure reducing system 120 of the intervention blowout preventer 1 may further comprise a pump 60 for pumping fluid from the cavity into the first chamber part as shown in FIG. 4. When equalising the pressure across the plug 37, the pressure in the cavity needs to be reduced. However, it may be necessary to force the fluid into the first chamber part by means of the pump 60 in order to reduce the pressure in the cavity and equalise the pressure across the plug.

In FIG. 5, the pressure reducing system 120 comprises an accumulator so that the chamber and the chamber is an accumulator. The accumulator comprises the piston, a bladder or a diaphragm. As shown in FIG. 5, the piston of the pressure reducing system 120 of FIG. 1 is replaced with a diaphragm 14

The intervention blowout preventer 1 may also comprise an accumulator as an additional pressure reducing system.

The intervention system may comprise a disconnection unit arranged between a lubricator valve and the intervention blowout preventer for disconnecting a part of the system, such as for disconnecting the lubricator and the intervention tool arranged inside the lubricator.

The intervention tool 100 may further comprise a driving section, such as a downhole tractor having wheels arranged on projectable arms, in order to anchor the tool inside the lubricator. Due to the pressure reducing system 120, the intervention tool needs not be anchored as much as prior art tools. The intervention tool 100 may be wireless and driven only by an internal power source, such as a battery.

The intervention blowout preventer 1 may often be arranged in a supporting structure in the form of a frame structure, and together with the frame structure it forms an intervention module. Furthermore, the intervention blowout preventer 1 comprising a control device on its outside enables a diver or the Remote Operational Vehicle (also called an ROV) to read and/or operate the control device in order to let fluid into the first chamber part 8, 108.

The control device may comprise a receiving and/or transmitting unit so that the control device has data transmission capability to a remote operating centre. The remote operating centre may thus be located in the nearest town and still be able to control a park of wells, and thus well heads 2, without viewing the control device. The intervention blowout preventer 1 may also comprise a control unit comprising a receiving and/or transmitting unit enabling the control unit to transmit data to and from a remote operating centre. Communicating with and receiving and/or transmitting data to and from the remote operating centre may take place by means of a satellite.

A motor, such as an electrical motor, may be arranged to operate the control device.

A stroking tool is a tool providing an axial force. The stroking tool comprises an electrical motor for driving a pump. The pump pumps fluid into a piston housing to move a piston acting therein. The piston is arranged on the stroker shaft 55. The pump may pump fluid into the piston housing on one side and simultaneously suck fluid out on the other side of the piston.

By fluid or well fluid is meant any kind of fluid that may be present in oil or gas wells downhole, such as natural gas, oil, oil mud, crude oil, water, etc. By gas is meant any kind of gas composition present in a well, completion, or open hole, and by oil is meant any kind of oil composition, such as crude oil, an oil-containing fluid, etc. Gas, oil, and water fluids may thus all comprise other elements or substances than gas, oil, and/or water, respectively.

By a casing is meant any kind of pipe, tubing, tubular, liner, string etc. used downhole in relation to oil or natural gas production.

In the event that the tool is not submergible all the way into the casing, a downhole tractor can be used to push the tool all the way into position in the well. The downhole tractor may have projectable arms having wheels, wherein the wheels contact the inner surface of the casing for propelling the tractor and the tool forward in the casing. A downhole tractor is any kind of driving tool capable of pushing or pulling tools in a well downhole, such as a Well Tractor®.

Although the invention has been described in the above in connection with preferred embodiments of the invention, it will be evident for a person skilled in the art that several modifications are conceivable without departing from the invention as defined by the following claims. 

1. An intervention blowout preventer (1) for being mounted on a well head (2) or a Christmas tree, comprising: a plurality of valves (3, 4) arranged in fluid communication with each other, connected and forming a tubular pipe (5) enclosing a cavity (10) being in fluid communication with the well head when the intervention blowout preventer is mounted onto the well head and at least one plug 37 in the well head has been removed, wherein the intervention blowout preventer further comprises a pressure reducing system (120) comprising a chamber (6) and a piston (7) arranged inside the chamber dividing the chamber into a first chamber part (8) and a second chamber part (9), the first chamber part being in fluid communication with the cavity and the second chamber part being filled with a compressible fluid, such as gas.
 2. An intervention blowout preventer according to claim 1, wherein the cavity has a first pressure and the intervention blowout preventer further comprises a control device (11), such as a valve, for controlling the pressure in the cavity by letting fluid in the cavity into the first chamber part.
 3. An intervention blowout preventer according to claim 1, wherein the piston is slidably arranged on a shaft (12) arranged inside the chamber.
 4. An intervention blowout preventer according to claim 1, wherein the first chamber part is connected with the cavity by means of a flow channel (15).
 5. An intervention blowout preventer according to claim 1, further comprising a control unit (38) comprising a storage device, and a communication unit for communicating with the control device.
 6. An intervention blowout preventer according to claim 1, further comprising a sensor for sensing a pressure in the cavity.
 7. An intervention blowout preventer according to claim 1, wherein the pressure reducing system further comprises a pump (60) for pumping fluid from the cavity into the first chamber part.
 8. An intervention blowout preventer according to claim 1, wherein the chamber is an accumulator.
 9. An intervention blowout preventer according to claim 1, wherein the pressure reducing system further comprises an accumulator.
 10. An intervention blowout preventer according to claim 8, wherein the accumulator comprises the piston, a bladder or a diaphragm.
 11. A well intervention tool (100) intended to be arranged in a lubricator for pulling a plug (37) in a top part (23) of a well head (2) or a Christmas tree of a well for entering the well, the well head having an axial extension, comprising: a connection pulling unit (50) having a connection unit (51) for connection to the plug, a stroking tool (52) having a tool housing (53) and being connected to the connection pulling unit and providing an axial movement along the axial extension, and a fixation unit (54) for fixating the stroking tool in relation to the well head so that the axial movement of the stroking tool pulls the plug out of the well head, wherein the stroking tool comprises a chamber (106) and a piston (107) arranged inside the chamber dividing the chamber into a first chamber part (108) and a second chamber part (109), the first chamber part being in fluid communication with an opening (113) in the tool housing and the second chamber part being filled with a compressible fluid, such as gas.
 12. A well intervention tool (100) according to claim 11, wherein the stroking tool further comprises a control device (11), such as a valve, for letting fluid in through the opening of the housing into the first chamber part.
 13. A well intervention tool (100) according to claim 11 wherein the connection pulling unit is a GS pulling tool.
 14. A well intervention tool (100) according to claim 11, wherein the piston is slidably arranged on a shaft (112) arranged inside the chamber.
 15. A well intervention tool (100) according to claim 11, wherein the control device is arranged in the opening.
 16. A well intervention tool (100) according to claim 11, wherein the stroking tool is connected with the connection pulling unit by means of a stroker shaft (55).
 17. A well intervention tool (100) according to claim 11, wherein the fixating unit comprises an anchoring section having anchors moving radially from the tool towards an inside wall of the lubricator.
 18. A well intervention system (200) comprising: an intervention blowout preventer according to claim 1 for connection onto a well head, a lubricator (20) connectable to the intervention blowout preventer, and an intervention tool (100) arranged inside the lubricator for pulling the plug (37) in a top part (23) of a well head (2) or a Christmas tree of a well for entering the well.
 19. A well intervention method comprising the steps of: arranging the well intervention tool (100) according to inside a lubricator, connecting the lubricator on the intervention blowout preventer, connecting the well intervention tool to the plug (37), equalising a pressure inside the cavity of the intervention blowout preventer with a pressure in the well below the plug, and pulling the plug (37) in a top part (23) of a well head (2) or a Christmas tree of a well. 